The honey bee queen lays an egg in a small chamber or cell in an area of the colony called the brood nest. A helpless, grub-like larva emerges from each egg after a few days, and its only function is to eat. Unlike a butterfly caterpillar that must forage for food, the bee larva never strays from its cell and nurse bees constantly deliver food, sometimes flooding the cell with food. It has been estimated that more than one hundred thousand visits are made to a single honey bee during its egg and larval stages, during which time the larva can increase in size one-thousand-fold. Because it doesn't leave its cell, the larva's bodily wastes are stored inside its body to protect the food in the cell from fecal contamination.
All honey bees outgrow their "skin" and molt about every twenty-four hours during the first few days of larval life. Their skin is actually an external skeleton or exoskeleton, and when the ecdysis or molting occurs, the skin splits at the head and slips off the rear end of the larva's body in a process that normally takes less than thirty minutes. Underneath is a new skin that is softer and looser at first, filling up as the larva grows until it is stretched tightly again, signaling that it is time for another molt. Each stage before the molt is called a numbered instar, and after the fourth instar has grown to its maximum size, several things happen.
Prompted by hormones and pheromones, the larva stops eating and finally expels its feces, which are pushed down to the bottom of the cell. The nurse bees apply a wax cap that closes off the cell, and the larva spins a cocoon around itself using silk from a special gland in its head. Layers of silk may coat the brood cell walls, having accumulated from previous larval generations. The beeswax that makes up the combs can soften in warm weather, and the accumulated silk is thought to strengthen the cell and give extra protection to the pupae.
Soon after the cocoon is complete, the fifth molt occurs inside the cocoon and the pupa is revealed under the old exoskeleton. During the pupal stage, the larva metamorphoses into a fully grown adult bee. When the metamorphosis is complete, the bee ecloses, which means it sheds its cocoon, and then finally leaves the cell to begin its adult working life. Beekeepers sometimes describe the emergence of the adult bees from the pupal case as "hatching," a colloquial term for eclosing.
The length of each developmental stage differs slightly for each caste, although each caste spends about three days in the egg. The queen spends eight days as a larva, and after about four days in the pupal stage she ecloses. Female workers spend about eight to ten days as larvae and eight days as pupae. Drones spend about thirteen days as larvae and eight days as pupae.
Nursing worker bees bring the larvae a series of different foods as they develop in their cells. At each stage of growth, the larvae give off particular chemical signals that tell the nurse bees what to feed them, resulting in qualitative and quantitative differences in the food given to larval queens, workers, and drones. The larvae that will develop into worker bees are first fed a brood food, also called worker jelly, which is produced by the hypopharyngeal gland in the head of a nurse bee.
After about six days, the nurse bees begin feeding the worker larvae a combination of nectar and bee bread, which is a substance made from pre-digested protein-rich pollen. After three more days, the larvae enter the pupal stage, at which time they stop eating and live off their accumulated body fat, and over the next few days they metamorphose into adult bees. The bee larvae that will develop into queens are fed exclusively on royal jelly for their first four days of life.
Drone larvae require the most food because they grow larger than either workers or queens, and the food mixture given to older drone larvae contains the most protein-rich pollen. Other species of bees have a different way of feeding their young. In solitary species there are no nest mates to care for the young. Instead, the mother prepares a nest in soil or in another small space and she places a small pellet of pollen mixed with freshly collected nectar in the nest. She lays one egg directly on this larder, and when the larva emerges it eats this food independently, without any contact with adult bees. It subsequently pupates, metamorphoses, and emerges as a fully developed adult bee.
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